# Docker Runtime Removal Documentation

## Overview

This document describes the complete removal of Docker runtime support from the Spear execution system. The Docker runtime has been replaced with Kubernetes runtime as the primary container orchestration solution.

## Changes Made

### 1. Runtime Type Enum Update
- Removed `RuntimeType::Docker` from the enum in `src/spearlet/execution/runtime/mod.rs`
- Updated all references to use `RuntimeType::Kubernetes` instead

### 2. Runtime Factory Changes
- Removed Docker runtime creation logic from `RuntimeFactory::create_runtime()`
- Removed Docker from `available_runtimes()` method
- Updated factory to only support Process, WASM, and Kubernetes runtimes

### 3. Module Structure Cleanup
- Removed `docker` module declaration from `src/spearlet/execution/runtime/mod.rs`
- Removed `DockerRuntime` and `DockerConfig` exports
- Deleted entire `src/spearlet/execution/runtime/docker.rs` file

### 4. String Mapping Updates
Updated string-to-runtime-type mappings in:
- `src/spearlet/function_service.rs`: Changed "docker" → `RuntimeType::Kubernetes`
- `src/spearlet/execution/artifact.rs`: Changed "docker" → `RuntimeType::Kubernetes`
- Added "kubernetes" → `RuntimeType::Kubernetes` mapping

### 5. Test Code Updates
Updated all test cases across multiple files:
- `src/spearlet/execution/runtime/mod.rs`
- `src/spearlet/execution/artifact.rs`
- `src/spearlet/execution/instance.rs`
- `src/spearlet/execution/task.rs`
- `src/spearlet/execution/runtime/process.rs`
- `src/spearlet/execution/runtime/wasm.rs`

All test instances that previously used `RuntimeType::Docker` now use `RuntimeType::Kubernetes` or `RuntimeType::Process` as appropriate.

### 6. Documentation Updates
- Updated module documentation in `src/spearlet/execution/mod.rs`
- Changed runtime support description from "Docker, Process, and WASM" to "Kubernetes, Process, and WASM"

## Supported Runtimes After Removal

The system now supports three runtime types:

1. **Kubernetes Runtime**: Container orchestration using Kubernetes
2. **Process Runtime**: Direct process execution
3. **WASM Runtime**: WebAssembly module execution

## Migration Guide

### For Existing Configurations
- Replace any `"docker"` runtime type strings with `"kubernetes"`
- Update any hardcoded `RuntimeType::Docker` references to `RuntimeType::Kubernetes`

### For New Deployments
- Use `RuntimeType::Kubernetes` for containerized workloads
- Use `RuntimeType::Process` for native process execution
- Use `RuntimeType::Wasm` for WebAssembly modules

## Testing Results

All tests pass successfully after the Docker runtime removal:
- 44 execution module tests passed
- Complete test suite (227 tests) passed
- No compilation errors or warnings

## Benefits of This Change

1. **Simplified Architecture**: Reduced complexity by removing redundant container runtime
2. **Better Orchestration**: Kubernetes provides more advanced orchestration features
3. **Industry Standard**: Kubernetes is the de facto standard for container orchestration
4. **Maintenance**: Reduced maintenance burden by focusing on fewer runtime types

## Future Considerations

- The Kubernetes runtime provides all the functionality previously offered by Docker runtime
- Container workloads should be migrated to use Kubernetes runtime
- The system architecture is now more aligned with cloud-native best practices